1. Field of the Invention
This invention relates to apparatus to be used in conjunction with a conventional electric drill for the precision drilling of holes in a workpiece.
2. Discussion of the Prior Art
Hand-held electric drills are versatile tools which find widespread utilization in various applications. Such drills are generally comprised of a high-speed motor enclosed within a housing having a gripping handle, and a chuck mounted on the motor shaft for engaging drill bits of various sizes. Although the portability and convenient handling of the hand-held electric drill are advantageous features, such features are not conducive to the precision or replicate drilling of holes as may be secured in factory operations using large drill presses.
Numerous auxiliary devices have heretofore been disclosed which seek to adapt the electric drill to improved precision of operation. In certain types of such auxiliary devices, the drill is mounted on a yoke-like carriage which slidably engages two opposed upright support columns attached to a base plate having an aperture centered beneath the drill bit. The auxiliary device of U.S. Pat. No. 2,997,900 to Pugsley further discloses a double base which functions as a vise for holding cylindrical workpieces such as pipes, and utilizes coil springs on said upright columns to provide an upward restoring force for the drill-carriage assembly. Although the device permits acceptance of drill bits of various sizes, the necessary adjustment for different length bits and hole depths causes variation in spring tension. The Pugsley device improves the precision of use of an electric drill but is limited to the drilling of holes perpendicular to the face of the workpiece, and further requires careful attachment of the drill to the carriage to ensure vertical alignment. The effort needed for such alignment causes the electric drill to lose its advantage of facile adaptation to varied tasks.
U.S. Pat. No. 3,874,810 to Russell discloses a drill guide apparatus generally similar to that of Pugsley except that a spindle is centered within the carriage member to achieve vertical alignment of an electric drill which attaches to said spindle. The upright columns of the Russell apparatus are adapted to pass adjustably and independently through a base plate to abuting engagement with an underlying workpiece. Such design is not compatible with the use of restoring springs, and does not afford sufficiently secure attachment of the apparatus to the workpiece for the precise drilling of holes.
It is an object of the present invention to provide a device adapted for use with a hand-held electric drill for improving the precision with which holes can be drilled in a workpiece, and containing springs which aid in restoring said electric drill to its position prior to the drilling of a hole in a workpiece.
It is a further object to provide a device of the aforementioned nature which can accommodate drill bits of various sizes and produce holes of various depths without significant variation of the restoring force provided by said springs.
It is another object to provide a device of the aforementioned nature which can be securely attached to the workpiece.
It is a still further object of this invention to provide a device of the aforementioned nature capable of drilling holes in a workpiece at angles between 45.degree. and 90.degree. with respect to the surface of said workpiece.
These objects and other objects and advantages of the invention will be apparent from the following description.